I think you're creating a universal here where there is none. I have secure boundaries, and I can enjoy a coworker's company and work without having to be friends with them. And there's also an ugly side to this, where people don't want to have coworkers that they wouldn't want to be friends with. That's not some natural urge, that's something that people impose on a situation that is alienating to people who don't share your politics, or your tastes, or even like the way you treat people (I'm referring to the hypothetical "you" here.)
I have really enjoyed working with people who I'd never want to know outside of work, and have a huge amount of respect for those people whose work ethic and trustworthiness showed a real thoughtfulness and concern about what they were doing and for their coworkers' time and development. That's good enough for me, we don't have to share musical tastes or hobbies. On the other side, I've certainly made friends with people at work, but some of the people I made friends with I hated working with. The two things are barely connected.